1. Field of the Invention
The present invention relates to recording method and apparatus using a process for communicating a bubble formed by utilizing thermal energy with atmosphere.
The present invention is applicable to printers for effecting the recording on a recording medium such as a paper sheet, a thread sheet, a fiber sheet, a cloth, a leather sheet, a metal sheet, a plastic sheet, glass, wood, ceramic sheet and the like, copying machines, facsimiles having a communication system, ETWs having keyboard input, and word processors, and to composite equipments.
Incidentally, in this specification and claims, a term "recording" means not only application of a significant image such as a character or a figure onto a recording medium but also application of a meaningless image such as a pattern onto a recording medium.
2. Related Background Art
Regarding practical recording methods applicable to various recent printers, an ink jet system in which a liquid droplet is formed by using a bubble generated by film-boiling caused by thermal energy (as disclosed in U.S. Pat. Nos. 4,723,129 and 4,740,796) is effective. Further, U.S. Pat. No. 4,410,899 discloses a recording method in which a liquid passage is not closed or blocked during generation of a bubble.
Although the techniques disclosed in the above U.S. patents can be applied to various recording systems, the above U.S. patents do not disclose or teach application to a system in which the recording is effected by communicating a bubble generated with atmosphere. Such a system is referred to as "atmosphere communication system" or "atmosphere communication type" hereinafter.
By the way, among the atmosphere communication system, an atmosphere communication system using rupture of the bubble does not provide stable liquid discharging, and, thus, is not practical.
Further, although a discharging principle is not known, a wishful phenomenon is disclosed in the Japanese Patent Application Laid-open No. 54-161935. In this technique, a cylindrical heater is disposed in each cylindrical nozzle so that the interior of the nozzle is divided into two by a bubble generated. In this arrangement, a liquid droplet can be formed, but, at the same time, a number of fine or minute liquid droplets are also formed due to "splash".
The Japanese Patent Application Laid-open No. 5-16365 discloses the invention in which the atmosphere communication system is improved up to a practical level.
The invention disclosed in the above Japanese Patent Application Laid-open No. 5-16365 aims to communicate a bubble generated for discharging an ink droplet from a discharge nozzle with atmosphere outside of the discharge nozzle in the vicinity of the discharge outlet. In the above Japanese Patent Application Laid-open No. 5-16365, a position of a thermal energy generating means for generating the bubble and pressure of the generated bubble are regulated or selected, and various parameters for communicating the bubble with the atmosphere under the regulated conditions, kind of liquid, configuration of the discharge outlet and a drive condition for generating the thermal energy are concretely specified. And, with the arrangement as mentioned above, the liquid discharging can be achieved with a good re-filling feature and without generating the splash and ink mist, and a recording apparatus having good frequency response and capable of providing a high quality image can be obtained. Further, since the bubble generated for effecting the liquid discharging is communicated with the atmosphere during the liquid discharging operation, a waiting time for disappearing the bubble in the liquid is not required, thereby achieving the high speed recording.
On the other hand, regarding liquid discharging techniques in which a bubble is generated and then disappeared in a liquid passage, U.S. Pat. No. 4,638,337 discloses the fact that the bubble is communicated with atmosphere in a nozzle due to retardation of a part of meniscus into the nozzle, thereby causing inconvenience. Incidentally, the above U.S. patent merely discloses the invention in which the bubble is surely generated and disappeared in the nozzle in order to eliminate a phenomenon that the bubble is communicated with the atmosphere in the nozzle due to the retardation of the meniscus into the nozzle.
Among the recording apparatuses of atmosphere communication type, in the recording apparatus disclosed in the above Japanese Patent Application Laid-open No. 54-161935, the discharging principle is not obvious, the practical level is not reached and it is difficult to put it to a practical use.
Although the invention disclosed in the above Japanese Patent Application Laid-open No. 5-16365 has the above-mentioned advantage, the following improvements may be desired to provide a recording apparatus having good frequency response and capable of obtaining a high quality image:
Firstly, since the bubble is grown outside of the discharge opening because a bubble generating portion is situated in the vicinity of the discharge opening, a volume of the liquid passage cannot be used effectively, with the result that a volume of the discharged liquid becomes smaller. This must be improved.
Secondly, since a bubble generating condition itself of the bubble generating portion for communicating the bubble with the atmosphere is greatly limited, an allowable design range of a recording head and kinds of liquids which can be used in the recording apparatus are also limited. This must be improved.
Thirdly, if the formation of the bubble is unstable in dependence upon change in environmental condition (for example, temperature, humidity and the like), since the unstable bubble formation directly affects an influence upon the communication between the bubble and the atmosphere, the unstable bubble formation affects an influence upon the discharged liquid (liquid droplet), thereby affecting an influence upon the recording. This should be improved.
Fourthly, regarding the discharging efficiency, there is energy loss. This should also be improved.
Lastly, since the re-filling feature cannot be improved, the frequency response is limited. This must be improved.